Engraving laser assemblies typically consist of a housing defining an engraving chamber for receiving a work piece. The engraving chamber generally comprises a lower surface which may support a work piece at the level of an engraving plane and a carriage operatively associated with one or more rails for axial movement along the rails, commonly referred to as movement along an X axis. The rails are typically movable as an assembly along a perpendicular Y axis. In this manner X and Y control motors can be actuated to move the carriage into operative association with the entire engraving plane.
The carriage is configured to direct a laser beam onto an object either resting on the lower surface or suspended in some manner within the engraving chamber under the carriage. As used herein “engraving plane” is intended to mean a plane onto which the laser is focused. For example, with a thin, flat work piece the “engraving plane” may essentially be the lower surface of the lasing chamber. For thicker work pieces the engraving plane may lie above the lower surface and correspond to a top surface of the work piece. As the carriage directs the laser beam onto a work piece received in the chamber, the beam selectively engraves the work piece. It is known to provide a concentrated stream of gas, typically air, from a nozzle attached to the carriage for the purpose of removing debris from the vicinity of the focused laser beam as the beam engraves a work piece and further to extinguish any flame that may result from the engraving process. Most typically this nozzle is connected to a coiled air supply tube extending from a sidewall of the engraving chamber to the nozzle. As the carriage is moved in an X direction along the rail and in a Y direction with the rail assembly, the nozzle moves with the carriage providing a stream of air to the focal point of the laser as the focal point moves during an engraving process. While such a configuration has the benefit of providing a focused stream of air at the focal point of the laser to clear debris and extinguish localized flames, if the carriage moves rapidly in the X direction it is possible that a flame ignited on the work piece will not be extinguished by the flow of air. In addition, with time the coiled supply tube has been known to fatigue and fail, creating maintenance issues. Further, the presence of the nozzle and the coiled supply tube associated therewith on the carriage increases the mass of the carriage requiring more robust motors and fittings to accommodate an increased dynamic load. This greater load also provides greater stress to components and may lead to less accurate positioning and component wear with extended usage of the engraving laser.
An alternative structure for providing air assist known in the art is providing a tube extending between rails of the rail assembly with axially spaced holes configured to direct a flow of air toward the engraving plane to remove work piece debris and extinguish flames. Such a structure has the advantage of minimizing mass of the X axis carriage, but adds additional mass to the rail assembly, providing an additional load on the Y control motor. Such a structure also simplifies air handling by eliminating the coiled tube and the nozzle on the carriage. In an effort to minimize weight on the rail assembly, these systems provide a thin walled tube for air delivery. However, such a tube is at risk for bending if inadvertently contacted.
The present invention is directed toward overcoming one or more of the problems discussed above.